Minimally invasive medical interventions are being used increasingly. Thus in the treatment of coronary heart disease for example surgical bypass operations on the heart are increasingly giving way to balloon dilatation (PTCA=percutaneous transluminal coronary angioplasty) and stent insertion. Minimally invasive interventions are also being used increasingly in the field of biopsies, spinal therapies and tumor ablations.
During a minimally invasive intervention one or more medical instruments is/are inserted for example into the body of a patient for therapeutic or diagnostic purposes. Once a medical instrument has been inserted into the body of the patient, it is no longer directly visible to a physician carrying out the intervention. To navigate the instrument in the body of the patient it must therefore be visualized appropriately for the physician in image information. Many different types of systems and methods are currently available to determine the position of the instrument in the body of the patient during minimally invasive medical interventions, as required to visualize the instrument, in particular the tip of the instrument, in image information from inside the body of the patient.
Progress in 3D x-ray imaging in the meantime allows 3D mapping of organs and also instruments in the body of a living being. However it is still difficult to distinguish between instruments, organs and bones in the x-ray image, while at the same time using as little x-ray radiation as possible for imaging and to determine instrument position.
In this context a method for determining the position and orientation of an object, in particular a catheter, in a patient based on two-dimensional x-ray images using so-called template matching is described in DE 10 2005 028 746 A1. A three-dimensional template of the catheter is produced here based on the known structural properties of the catheter. To determine the position and orientation of the catheter in the body of a living being the three-dimensional template is projected onto a two-dimensional plane and the projection image produced is compared with an x-ray image, in which the catheter is mapped. Parameters determined initially for the position and orientation of the template in space are then modified iteratively and a degree of similarity is determined, which is used to determine the position and orientation of the catheter.
An electromagnetic navigation system AURORA from the company NDI, Waterloo, Ontario, Canada is described in “Needle and catheter navigation using electromagnetic tracking for computer-assisted C-arm CT interventions”, Markus Nagel, Martin Hoheisel, Ralf Petzold, Willi A. Kalender and Ulrich H. W. Krause, Medical Imaging 2007: Visualization and Image-Guided Procedures, edited by Kevin R. Cleary, Michael I. Miga, Proc. of SPIE Volume 6509, 65090J, (2007) 1605-7422/07/$18 doi: 10.1117/12.709435. The electromagnetic navigation system comprises a field generator for generating an electromagnetic field, to determine positions and orientations of medical instruments, each having small induction coils at their tip. The AURORA system can use the induced voltages to determine the position and orientation of the respective instrument.
To improve the accuracy of instrument location and to improve the determination of the coordinate transformations between an image coordinate system and a coordinate system assigned to the navigation system, also referred to as registration, navigation systems based on x-ray radiation and/or on electromagnetic waves frequently have a plate comprising x-ray markers and/or electromagnetic markers, which is disposed below a patient, on whom the minimally invasive intervention is carried out. Thus the system described in “Needle and catheter navigation using electromagnetic tracking for computer-assisted C-arm CT interventions”, Markus Nagel, Martin Hoheisel, Ralf Petzold, Willi A. Kalender and Ulrich H. W. Krause, Medical Imaging 2007: Visualization and Image-Guided Procedures, edited by Kevin R. Cleary, Michael I. Miga, Proc. of SPIE Volume 6509, 65090J, (2007) 1605-7422/07/$18 doi: 10.1117/12.709435 has a so-called registration panel with five x-ray markers, which can be detected automatically in x-ray images, and with an electromagnetic sensor, which can be detected using the AURORA system. The registration panel is not only used for registration here but also as a reference system during the navigation of instruments.
One disadvantage of this solution is that the plate registration panel comprising the x-ray markers and the electromagnetic marker or is uncomfortable for the patient and can cause the patient to suffer bruises or pressure sores during longer interventions.
The field generator of the electromagnetic navigation system must also be secured to a patient support apparatus holding the patient or be disposed on a separately embodied stand adjacent to the patient support apparatus, in order to provide the electromagnetic field for navigation in the desired spatial region. However this structure hinders access to the patient and also increases the risk of collision, for example with a medical imaging device used for interoperative imaging during the intervention.
The electromagnetic navigation system also has a PC (personal computer) with a display apparatus on a cart or rack to operate the electromagnetic navigation system. The cart or rack also takes up space around the patient support apparatus.
Also patient administration and the documentation of navigation-assisted interventions including the recording of consumables used during such a medical intervention is not integrated due to the different items of equipment and individual components used, which is disadvantageous for the most optimal medical workflow possible, as data relating to a medical intervention, e.g. patient data, must be managed, input, modified, transferred to a patient file, etc. both at the electromagnetic navigation system and also at the imaging device used.